Cut a strip of paper. Almost any size will work.
Valley fold the corner at a 45 degree angle to form a triangular flap.
Valley fold along the edge of the triangular.
Repeat folds five to seven times. Make a small valley fold on the corner and tuck this section of paper under one of the existing layers. It will look like a tightly wrapped triangle.
Cut the corners with a sharp scissors.
Use your thumbnail or a hard sharp object to push a dent along the wide edge of the triangle.